That's a good question.. they are giving people an additional 90 days right!? They are expecting it. So if you send your application without your exams, they will probably return it and give you more time, based on the pandemic based schedules.
In my case I will wait one or 2 months before sending without it.. see how far this thing goes! Unless someone knows any other way around.
As already stated, IRCC is not returning apps that are missing things due to COVID-19 closures.